The following relates generally to wireless communication and more specifically to secondary timing advance groups (sTAGs) with only license assisted access (LAA) secondary cells (SCells).
Wireless communication systems are widely deployed to provide various types of communication content such as voice, video, packet data, messaging, broadcast, and so on. These systems may be capable of supporting communication with multiple users by sharing the available system resources (e.g., time, frequency, and power). Examples of such multiple-access systems include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, and orthogonal frequency division multiple access (OFDMA) systems, (e.g., a Long Term Evolution (LTE) system, or a New Radio (NR) system). A wireless multiple-access communications system may include a number of base stations or access network nodes, each simultaneously supporting communication for multiple communication devices, which may be otherwise known as user equipment (UE).
Some wireless communications systems may utilize timing advance techniques to align uplink transmissions from multiple UEs to a base station. In particular, a UE may identify a timing advance and a downlink reference time, and the UE may transmit to a base station based on the timing advance and the downlink reference time such that the uplink transmission is aligned with other uplink transmissions from other UEs. The UE may determine the downlink reference time based on a downlink transmission received from a base station. In some cases, however, a UE may not receive a downlink transmission from a base station, and, as a result, the UE may not be able to determine a downlink reference time for an uplink transmission. In such cases, the UE may be forced to suspend the uplink transmission, which may result in additional latency and reduced throughput in a wireless system.